


The Odd Sis Out

by fox_ghost



Category: Teenage Mutant Ninja Turtles - All Media Types
Genre: Gen, Sister - Freeform, little sister - Freeform, secret sister
Language: English
Status: In-Progress
Published: 2019-09-01
Updated: 2019-09-01
Packaged: 2020-10-04 13:37:46
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 1,801
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20471918
Author URL: https://archiveofourown.org/users/fox_ghost/pseuds/fox_ghost
Summary: The Teenage Mutant Ninja Turtles have a little sister that fate meant for them to have. Sorry, this is a terrible summary and a terrible title. I'm new at this.





	The Odd Sis Out

**Author's Note:**

> Hi, everyone. This is my first fanfiction ever!!! Sorry about the terrible title and summary. Like I said, I'm new at this. I'm open to suggestions on the title and how to improve the summary. I'm letting you know now, I've written the whole story before hand. CONSTRUCTIVE CRITICISM IS CRAVED FOR!!!! This story is to help improve my writing, and also because I want to write more fan fiction for other fandoms, so this is a practice. Enjoy!!!  
P.S. If this doesn't get many views or somewhat-ok reviews, I'm not going to post other chapters.

This is my story. A side to one story that you've never heard before. You’ve all heard of the famous Teenage Mutant Ninja Turtles. The ones that save the city and the world from threats like the Kraang and Shredder. But you’ve never heard of one of their greatest secrets. The secret that they want to keep hidden from everyone, especially their most hated enemy. 

And that secret would be me. Their little sister. I haven’t been part of their family long, only 2 years, and I’m the outcast. They try to include me in everything they do, except going to the surface. They never let me leave home and I don't feel like leaving. This is the first real home that I've had. The hole I lived in for half of my life doesn't count. Now I bet you're wondering how I came to be. It’s kind of a long story, so I’ll try to shorten it. 

Everyone at TCRI was obsessed about how the mutagen affected the turtles and wanted to learn more. So they tried to make another one. Somehow, they got their hands on a lot of mutagen. When I was locked up, I saw an entire room full of it. 

They bred many Red-Eared Sliders and splashed mutagen on them when they became infants. I was the first successful mutant that didn’t have any side-effects. I can only imagine the horrors that came upon the ones that weren’t so lucky.

I was under lock and key for 5 years. Studied in every aspect the “scientists” could think of. My cell production, digestion, brainwaves. They hooked me up to machines, starved me to see how long I could survive without food. The same with water. And many more experiments that I would prefer not to mention. Until, I got fed up one day with how I was treated. I broke out, caused a mass panic, and hid in the sewers. That’s where I stayed, for three years, hiding from the world. During that time, I sort of trained myself how to hide. I had to hide from people who came to the sewer, and in case the people from TCRI came looking for me. I taught myself how to walk without making a sound, how to sneak around the sewers without being detected, especially in the water. I can step without making a splash. When I walk on pipes, they don’t even creak. 

I found the TMNT about a year and a half after I freed myself. At first, I was terrified of them. Then I realized they were just like me. I became fascinated with them; how they moved, how skilled they were with their weapons. And how much of a bond they had with each other. So I followed them whenever I could. I eventually found their lair, but didn’t go much further than that. I did that for the years leading up until they saw me for the first time. 

I was sleeping in my hole when I heard it. The creak of pipes giving out. I couldn’t get out of my home before the ceiling came crashing down on me. I tried to free myself after waking. When I shifted though, fire shot up my ankle. I looked down. It was at an angle that wasn’t normal. Great, it’s broken. No matter how much I tried to get myself unstuck, I couldn’t get myself. I had no choice but to lay there. 

They found me a couple days later, near death. I overheard Don say I was dehydrated and malnourished. I recovered fast, faster than I thought I would. I didn’t know why, and I didn’t care. I was just happy I wasn’t dead.

When I finally met Don’s health seal of approval, they tried to ask me questions about where I came from; how I ended up stuck under 300 pounds of solid rock, and anything and everything that came to their minds. But I didn’t answer.

I learned how to talk by listening to the scientists who were around me 24/7. I never talked to them though. What was the point? I had nothing to say to them. Also, I didn't really trust them. Sure they saved me, but I couldn’t be 100% sure that they did it out of kindness or they wanted something out of me. 

So that’s how it was for the next week. Them asking a lot of questions, and me not answering. Me trying to find every possible hiding spot that I was sure they would never find me in. Everytime I thought I found one, Mikey, which I guessed at the time was the youngest and the most immature, would show up. I eventually found one, high up in the wall, that looked like it had never been touched. And I was right. Every time I thought Mikey would show up, he didn’t.

After a month, it was safe to say I was part of the family. I was treated like one of them, and as a living thing, not a successful experiment. This was also the time that they decided to see if I had the potential for ninjutsu. Leo brought me into the dojo, where Splinter and the rest of my “brothers” were kneeling, all facing me. Leo sat me down and went and stood next to Splinter.

“Do not worry, my child, you are not in trouble. We have all come to a decision about how to progress further. Leonardo will explain.” This scared me even more. How to progress further? Were they finally going to kick me out? I studied their faces. None of them had any look or any physical indication that that’s what Splinter was referring to. I looked back at Leo. he had a soft expression on his face, so I knew nothing bad was going to happen. 

“As you know, young one, you have been with us for about a month. We treat you as a sister and would like to continue to have you as part of our family. Do you agree?” I stared at them and thought for a little. I finally have a family. One that treated me well. And they could protect me from my previous captores if they ever come for me again. So I nodded.

“Good. Then comes the tricky part. We have to come up with a name for you.” That part I didn’t expect. A name? I’ve never had a name. Why would I need one? I always expected that they would keep calling me “young one” and “little sis”. Splinter interjects. “I might have a solution for this problem.” He grabs a book out of his robe. All four of my brother gasp. Seems this book means something to them.

“Is that...” Mikey trails off. “It is my son,” Splinter responds. “It is the book that I found the names for all four of you. And since it brought such luck to us before, it might bring us luck once again.”

He waved me over and I sit next to him. He opens the book and flips to the female section. “When you see a name that you like, point it out, and we will go from there.” He slowly turns the pages, giving me time to study every name, what it means, and what that woman did. He continued to flip, and I continued to read, but I couldn’t find one that I liked. He finally stopped. “This is the last page, young one. I hope you can find a name on this one.”

He turned it over and I looked. It was the last woman on the page. She was tucked away in the corner, so little writing next to their picture you might have skipped over it. But I didn’t. She wasn’t the most beautiful woman, but I loved her name. I stuck my finger at her picture and Splinter learned over to look at it. He smiled. “I like that name. It suits you.”

Everyone else leaned over to look at the name. After reading it, everyone agreed. Except Raph. he didn’t say anything, and knowing him, it probably meant he didn’t like it and was expecting more of a badass name.

I finally had a name. An identity. I was jumping up and down inside, but showed no emotion on the outside. What was the point? They already knew I liked it. 

“Catharina it is,” said Leo. He smiled. “Now that we have that dealt with,” began Splinter, “we had one other thought.” he looked down at me. “Would you like to learn ninjutsu?” My mouth fell open, but I snapped it shut. I would have to think about this one. So I shrugged. “We’ll give you some time to think about it, of course,” Donnie butted in. “You have to let us know soon so we can start. You’re a far way behind the rest of us.”

I sat there thinking about it, so deep in my thoughts, I didn’t notice any of them leave the dojo. Soon I was the only one there, sitting in the middle of the room, staring at the floor. Do I want to learn? It would be cool to learn. And I would be able to protect myself if the TCRI guys ever came after me. But could I ever live up to the rest of them? They’ve been doing this much longer than I have and have way more experience. Would I ever be as good as them? I must have sat there for hours because the place was quiet. Everyone must have already gone to bed. 

I walked over to the couch , where my makeshift bed was. It was mine until they could find another hole in the sewer that wasn’t being used. Donnie offered to move his lab, but I shook my head. He loved that place. It was his private little area. I wouldn’t take that away from him. I laid down on it and pulled the covers up to my chin and fell asleep straight away. 

A week passed before I agreed to start training. Turns out. I was a natural. Even more than Mikey. I mastered everything physical they had learned in 16 years in less than a week. Then Splinter let me spar with them. I’m pretty sure Leo was jealous when I beat him in the first minute. 

After that, we started with the weapons. I mastered those in two. I surpassed them in that field as well. Now for this, I’m sure Raph was pissed. I could see the anger in his eyes. He didn’t act on it though. That made me happy. 

Now that you know most of my backstory, I can finally move on.

**Author's Note:**

> Thanks again for reading. Once again, I CRAVE CONSTRUCTIVE CRITICISM!!!! And let me know if you have better ideas for the title and summary.


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